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NASA -- NASA Image Of The DayWilliam Smith's Geological Map of England: Image of the Day (2008)

Before the late eighteenth century, residents of England didn't necessarily take much interest in the rocks under their feet. The arrival of the Industrial Revolution, however, drew the attention of the country's entrepreneurs downward. England's industrialists began plunging deep underground for coal -- the fossilized remains of ancient swamps -- and carving canals across the countryside to transport it efficiently. In this environment, a geologist named William Smith managed to marry his knowledge of rock layers with his love of fossils.

The eventual outcome of Smith's research was A Geological Map of England and Wales and Part of Scotland, first published in 1815. On a scale of 5 miles per inch, the map measured 6 feet by 8 feet 6 inches. It was not the world's first geologic map, but it was the first to map such a large area in such detail.

In mapping rocks that lay underground, Smith faced a challenge. He had to relay three dimensions of information on a two-dimensional surface. Near the end of the eighteenth century, he had seen an agricultural map that used color coding to indicate soil type, and he borrowed that convention for his map of rock layers, or ''strata.'' Color gradations showed where one rock formation gave way to the next. Smith supplemented the surface map with a cross section of rock layers (middle right).

To distinguish rock layers, geologists rely on several factors, such as color, hardness, and slope. Smith added an important new criterion: fossils. Because species change over time, the fossils they leave behind also change. Smith did not grasp the concept of evolution, but he did understand that changes in fossil assemblages could be used to order rock layers. His discovery became known as the principle of or

In the more than 150 years that have elapsed since Smith's death, scientists have developed rock-dating techniques based on the rates of radioactive decay of atoms. pubs.usgs.gov/gip/geotime/radiometric.html Radiometric dating gives absolute dates to some kinds of rocks and organic materials -- the age of our planet is estimated at 4.6 billion years -- but most fossil-bearing, sedimentary rocks (rocks created by erosion) cannot be dated radiometrically. To estimate the ages of these rocks, geologists and paleontologists continue to rely on Smith's principle of faunal succession.

To learn more about Smith's life and the legacy his scientific discoveries, please see the feature article earthobservatory.nasa.gov/Library/Giants/WilliamSmith/ William Smith (1769-1839).

Map reproduced by permission of the www.bgs.ac.uk/ British Geological Survey. ©NERC. All rights reserved. IPR/100-28DR. To obtain a copy of the map, visit the BGS shop.bgs.ac.uk/ online shop. ) Caption by Michon Scott.

This item is part of the collection: NASA Images

Identifier: strata_england_wales_1815
Filename: strata_england_wales_1815.jpg
Creator: NASA -- NASA Image Of The Day
Date: 2008
Mediatype: image
Rights: Public Domain
Source: http://earthobservatory.nasa.gov/IOTD/view.php?id=8733
Year: 2008
Publicdate: 2011-07-18 09:30:53
Addeddate: 2011-07-18 09:30:53
Language: English
Keywords: What -- GRASP

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Reviewer: potsmoke66 - 3.00 out of 5 stars3.00 out of 5 stars3.00 out of 5 stars - July 22, 2012
Subject: a poor fellow
it seems it's not enough that his work has been plagiated, no, even to find anything about his life isn't easy. fortunately archive.org exists and the link to the nasa earthobservatory.

hasn't he deserved a better reputation over all?

there was once a documentary on german television (zdf), but even this has vanished from their archive.